Delta

McDonnell Douglas Commercial Delta, Inc.

5301 Bolsa Avenue, Huntington Beach, CA 92647

(714) 896-3311

The Delta II is an expendable launch vehicle currently used to launch Navstar
Global Positioning System satellites into orbit. These satellites provide
navigational data to military and civilian users. Additionally, the Delta II
launches civil and commercial payloads into low-earth, polar, geo-transfer and
geosynchronous orbits. Various Delta configurations have successfully launched
170 spacecraft to orbit as of June 1988. Incremental growth of the Delta over
the years has increased its lift capacity to LEO from several hundred to 8,000
pounds.(1)

A Thor is a Thor is a Thor ... unless it has been employed as the first stage of a
Thor-Delta space vehicle. In that case it could be a Thrust Augmented Thor, or
a Long Tank Thor, or any of a number of different booster configurations which,
since May of 1960, have provided the initial thrust for NASA and DOD space
launch vehicle. The Delta launch vehicle family began in 1959 when NASA's
Goddard Space Flight Center awarded a contract to Douglas Aircraft Company
(now McDonnell Douglas Corporation) to produce and integrate 12 space-launch
vehicles. The Delta used components from the US Air Force's Thor
Intermediate-Range Ballistic Missile program as its first stage and the US
Navy's Vanguard launch-vehicle program as its second. The first Delta, with an
Echo I communications satellite on board, was launched from Cape Canaveral
Air Force Station on May 13, 1960.

Through the years, as missions became more complex and launch vehicle
requirements more exacting, the Thor-Delta possessed the flexibility to
accommodate the variety of missions assigned to it. The vehicle's long use stems
from this tradition of adaptability through its "building block" configuration. The
Thor-Delta has evolved through a large number of configuration changes. This
evolutionary process has been and is a continuing one. The Thor-Delta launch
vehicle experienced a consistent evolutionary growth since its initial launch in
1960. Through this growth, averaging one major change each year, the vehicle
was able to keep pace with the various US space efforts, with payload
requirements that were constantly changing.

When larger payloads called for a more powerful vehicle, the Air Force and
McDonnell Douglas introduced the Improved Thor-Delta and the Thrust
Augmented Delta. NASA contracted with the Air Force for the use of the Thor
booster, while the Delta second stage vehicle was produced directly for NASA by
McDonnell Douglas, which was awarded the initial contract for the vehicle in
April of 1959. In both instances, utilizing previously developed improvements
proven by Air Force configurations, three solid propellant motors were attached
to the booster's base to provide increased thrust for the first part of flight.

Thor DM18/3 - The first stage of the two-stage Thor-Agena A launch vehicle
was a Model DM-1812-3 Thor (essentially a Model DM-18A modified by the
removal of the nose cone and guidance, which was incorporated in the second
stage). The second stage was a Lockheed 2205 Agena A powered by a Bell
Aircraft Hustler liquid-propellant engine. The Thor-Agena A was used for the
first time on 28 February 1959, with the 1300-pound spacecraft Discoverer 1,
carrying a payload twice as heavy as any previous one carried by an American
launch vehicle. The performance of the initial Thor-Agena A was flawless
throughout the flight, and Discoverer 1 was successfully placed into a polar
orbit, the first such orbit ever effected by a United States spacecraft. The last
Thor-Agena A launch occurred on 13 September 1960, with Discoverer 15 was
successfully placed into orbit.

Thor DSV-2B -- The two-stage Thor-Ablestar (Thor-Epsilon) launch vehicle
employed two Thor model booster configurations: the DM-21A; and the DSV-6.
Both configurations were essentially DM-21's with a new adapter section,
forward of a transition section to accommodate the second stage. The Model
DM-21A Thor-Ablestar combination was used for launching various
earth-orbiting navigational, scientific, geodetic, and communications spacecraft,
including those in the Transits Courier, and ANNA series. The added Ablestar
stage was developed by Ramo-Wooldridge and Aerojet-General and later
produced by Space-General. It featured the first liquid-propellant restartable
engine which could stop and start once or twice in space. All previous upper
stages in Thor-launched vehicles reached full burnout, having no capability of
refiring under space conditions. By cutting off and restarting as much as 20
minutes after the launch sequence had ended, the Ablestar was able to "correct"
its orbit, making it more circular or elliptical as the case might require.

Thor DSV-2S - The first stage of the two-stage Thor-Burner I launch vehicle
was a Model DM-18A. The second stage was a Thiokol FW-4 TE 364-1 Burner I
solid propellant rocket motor.

Thor DSV-6 -- The two-stage Thor-Ablestar (Thor-Epsilon) launch vehicle
employed two Thor model booster configurations: the DM-21A; and the DSV-6.
Both configurations were essentially DM-21's with a new adapter section,
forward of a transition section to accommodate the second stage. The Model
DSV-6 Thor-Ablestar combination was used to place various Air Force and Navy
classified payloads into orbit.

Thor PG-2A - The Discoverer satellite launches by no means came to an end
with the last Thor-Agena A flight. The missions were simply continued with a
new launch vehicle, the Thor-Agena B, which was an improved version of the
Thor-Agena A. The booster for the vehicle was a Model DM-21 Thor, basically a
Model DM-18C with a higher thrust engine, nose fairing removed, and guidance
section replaced by a shorter, lighter transition section. The second stage was a
Lockheed 8096 Agena B, similar to the Agena A, but with larger propellant
tanks and an engine with restart capabilities. The new vehicle started its career
with the Air Force on 26 October 1960, when it was used to launch Discoverer
16, but the Agena B vehicle failed to separate and the spacecraft, of course,
never achieved orbit. But on 12 November Discoverer 17 was successfully placed
into orbit.

Thor LV-2F - The first stage of the two-stage Thor-Burner II launch vehicle was
a Model DM-18A. The second stage was a Thiokol TE 364-2 Burner II solid
propellant rocket motor.

Thor SLV-2A - The Thor-Agena D was first used on 28 June 1962 to launch a
classified Air Force payload from the Western test Range. Its immediate
successor was the Thor-Agena B, which used the same first-stage Model DM-21
and DSV-2A Thor boosters but earlier models of the Agena stage. The lift
capability of the vehicle was significantly increased when the new Model
DSV-2C, or Thrust Augmented Thor, was introduced into the launch system, on
28 February 1963. That Thor configuration incorporated three solid-propellant
motors which produced an additional 161,550 pounds of thrust and dropped off
after burnout. Minor changes were made in the engine section structure and in
the control circuitry to accommodate the solid motors.

Thor SLV-2G - The Model DSV-2L series booster, or Thrust Augmented Long
Tank Thor, made its first appearance in the Thor-Agena D system on 9 August
1966, when it was used to launch a classified Air Force payload. The new
booster was basically a DSV-2A with liquid propellant capacity increased 43
percent and augmented with three Thiokol TX354-5 solid propellant motors, each
of which provided an additional 51,490 pounds of liftoff thrust. The launch
vehicle was thus capable of placing a greater spacecraft weight in orbit than
ever before. In the DSV-2L configuration, a transition section housing the flight
control equipment, electrical power components, and an umbilical connection
assembly is permanently attached to the forward end of the booster adapter
section to provide mounting capability for the Agena D second stage, which
carries the payload. The Thor-Agena D vehicle has been used primarily by the
Air Force to launch classified payloads.

Delta 2914 - The model DSV-2W was produced by McDonnell Douglas as the
first stage of a Model 2000 series Straight Eight Delta Launch Vehicle. The
"Straight Eight" designation referred to the vehicle's constant 8-foot diameter
from base to nose curvature. The Straight Eight* vehicle provided a much
expanded spacecraft fairing envelope and a sizeable increase in payload weight,
utilizing previously flight-proven components. With versions developed for both
two- and three-stage requirements, it offered choice of vehicle for each specific
mission, placing spacecraft into low earth orbits, by either a direct ascent single-burn or Hohmann transfer dual-burn flight mode. The three-stage configuration
was suited for missions which placed spacecraft into highly elliptical earth orbits
or for high-energy missions involving synchronous satellites. The Straight Eight
launch vehicle was first used on 9 November 1973 by NASA to launch Telesat
Canada's Anik-l TV-telephone relay satellite. The DSV-2W first stage included a
repackaged Rocketdyne H-l single-start, liquid bipropellant main engine,
designated a Model RS-27; two vernier engines; and the attach fittings for either
three, six, or nine Castor II strap-on solid propellant motors. The interstage
assembly extended from the top of the first stage to the second stage mini-skirt
and encapsulates a portion of the second stage. The second stage included an
Aerojet AJ10-118F liquid bipropellant engine with fixed calibrated thrust and
multiple restart capability, and a digital inertial guidance system. The third
stage used either a Thiokol TE 364-3 or TE 364-4 solid propellant rocket motor.

Delta 3920 - The Delta 3900 series replaced the Castor II motors with larger
and more powerful Castor IV motors. A typical 3900 series Delta weighed
193,233 kilograms at lift-off and developed 2,807 kilonewtons of thrust.(3)

Delta Designators

In 1972 a four-digit number replaced the alpha-numerical designations
previously used. The numbers in the four-digit code designator for Delta are:(4)

The Delta launch vehicle has been continually upgraded through the years in
response to the need for increased payload capability. The most advanced Delta
configuration preceding Delta II was the Delta 3920/PAM which had a 100%
success rate. This design was upgraded in two phases to provide Delta II
performance capabilities: Delta II 6925, with a 14% increase in geosynchronous
transfer orbit (GTO) capability, and Delta II 7925, with a further 26% increase.

Delta II 6920 Series

In January 1987 the Air Force awarded a contract to McDonnell Douglas for
construction of 18 Delta IIs to launch Navstar Global Positioning System
satellites, originally programmed for launch on the space shuttle. Since then, the
order expanded to accommodate 28 Global Positioning System satellite-dedicated
launch vehicles. The first Delta II 6925 was successfully launched on 14
February 1989, at Cape Canaveral AFS, FL.

Initial improvements incorporated into the Delta II 6925 vehicle included a 9.5-ft
(2.9 m) fairing to accommodate larger spacecraft, a 12-ft (3.66 m) extension in
the first-stage tanks for added propellant capacity, and the use of higher
performance solid rocket boosters - the Morton Thiokol Castor IVAs. Thrust
augmentation is provided by these nine unsegmented solid propellant rocket
motors, six ignited at liftoff and the remaining three ignited in flight.

The first stage has an engine section that houses the Rocketdyne RS-27 main
engine, two Rocketdyne LR101-NA-11 vernier engines, and provides the aft
attachments for the strap-on solid propellant motors. The cylindrical isogrid
RP-1 fuel and liquid oxygen tanks are extended 4.7 ft (1.43 m) and 7.3 ft (2.23
m), respectively, beyond the 3920 configuration. The two tanks are separated by
a center body section that houses control electronics, ordnance sequencing
equipment, and a telemetry (T/M) system. The RS-27 is a single-start, liquid
bipropellant rocket engine with a thrust rating of 207,000 Ib (921 kN) at sea
level. The two vernier engines provide roll control during main-engine burn, and
attitude control after cutoff and before second-stage separation. A rate gyro has
been added to the first stage, forward of the center body section, to assure
adequate stability margins with the extended tanks and larger fairing.

The Delta interstage assembly extends from the top of the first stage to the
second-stage miniskirt. This 15.5-ft (4.72 m) long isogrid structure carries loads
from the second stage, third stage, spacecraft and fairing to the first stage, and
contains an exhaust vent and six spring-driven separation rods.

The second stage uses the restartable Aerojet AJ10-118K engine developed for
the Air Force Improved Transtage Injector Program (ITIP), and uses nitrogen
tetroxide and Aerozine-50 storable propellants. Gaseous helium is used for
pressurization, and a nitrogen cold gas jet system provides attitude control
during coast periods and roll control during powered flight.
Hydraulically-activated gimbals provide pitch and yaw control. An isogrid
configuration equipment panel is attached to the aft section. The forward section
of the second stage houses guidance and control equipment that provides
guidance sequencing and stabilization signals for both first and second stages.
The Delta inertial guidance system (DIGS) is a strap-down all-inertial system
consisting of a Delta redundant inertial measurement system (DRIMS) and a
Delco guidance computer (GC). The DRIMS contains three gyros, four
accelerometers, and conditioning electronics. DRIMS data is processed in the
computer to obtain attitude reference and navigation information. The computer
also issues preprogrammed sequence commands and provides control system
stabilization logic for both powered and coast phases of flight. Electronic
packages in both first and second stages receive commands from the GC, and
drive the servo amplifiers for engine gimbal and the switch amplifier for control
jet (vernier or gas jet) operations. Both first and second stages have a
battery-supplied DC power system. Separate batteries are used for the guidance
and control system, ordnance, engine systems. The instrumentation and flight
termination systems are powered by the same battery. The vehicle also contains
a T/M system and a range-safety tracking system.

The vehicle's third stage is derived from components and concepts used on the
Delta third-stage and the Air Force SGS-II upper stage. The Star-48B
solid-rocket motor is supported at the base of the motor on a spin table that
mates to the top of the second-stage guidance section. The payload attach fitting
(PAF) structure provides the transition from the top of the solid-rocket motor to
the spacecraft interface. Before third-stage deployment, the stage and spacecraft
are spun-up using spin rockets rotating the assembly on a spin bearing. Variable
spin rate is achieved by selecting rockets from an inventory of different size,
qualified spin rockets.

The final vehicle element is the Payload Fairing (PLF), which shields the
payload from buffeting and aerodynamic heating while in the atmospheric phase
of flight. The aluminum structure, which incorporates acoustic absorption
blankets on its interior, accommodates the spacecraft envelope. Fairing halves
are separated by a flight-proven contamination free separation joint. The aft end
is identical to the present Delta 8-ft isogrid fairing to maintain the same
second-stage interface. The center section, aluminum skin-stringer construction
similar to fairings currently being constructed by McDonnell Douglas Space
Systems Company (MDSSC) for Titan vehicles, increases the envelope to
accommodate the global positioning satellite (GPS) spacecraft, and also provides
increased flexibility for the commercial user.

Delta II 7920 Series

The Delta lI's second version, Delta 7925, began boosting remaining GPS
satellites on 26 November 1990. The Delta II 7920 has a 12-foot longer first
stage than previous Delta vehicles. Nine Hercules Aerospace strap-on
Graphite-Epoxy Motors (GEMs) surround the first stage for augmented lift-off
with a thrust of 45,000 kiloNewtons. Containing a more powerful propellant
mixture than did its predecessor, the motors are built in a composite material
called graphite-epoxy which is lighter but as strong as the steel cases they
replaced. The new motors are 6 feet longer and provide 40 percent more thrust.
Thrust is aided by the unsegmented solid-rocket motors as six ignite at lift-off
and the remaining three are ignited in flight.

The first stage includes one Rocketdyne RS-27 and two LR-101-NA-11 vernier
engines; both use RP-1 (refined kerosene) and LO2 (liquid oxygen) as its
propellants, with a thrust of 101,250 kiloNewtons. The second stage is a
restartable Aerojet AJ10-110K motor using N2O4 (nitrogen tetroxide) and A50
(Aerozine 50) propellants with a thrust of 4,050 kiloNewtons. The payload assist
module, if used, is a Star-48B solid-fuel rocket with a 6,750 kiloNewton thrust.

Height in position is 125 feet (37.5 meters), and the diameter is 8 feet (2.4
meters). With a gross lift-off mass of 227,700 kilograms, the Delta II can carry
payloads into near-earth orbits (approximately 160 kilometers in space). It can
lift up to 4,995 kilograms into a 28-degree circular near-earth orbit and up to
3,789 kilograms into a 90-degree polar near-earth orbit. The Delta II also can
carry up to 1,805 kilograms into geo-transfer orbit (approximately 19,200
kilometers) and up to 900 kilograms into geosynchronous orbit (approximately
35,200 kilometers). Payloads include the Navstar Global Positioning System as
well as NASA's MELV, Radarsat and Lageos, and commercial tasks such as
Inmarsat, Palapa, ASC-2, and NATO communications satellites. The guidance
System is the Delta redundant inertial measurement system and a Delco
guidance computer.